Mourners gathered in the courtyard between the cemetery's former chapel, now its offices, and the cemetery's colonnade.

Litvinenko's coffin, a dark-stained Jacobean oak Garratt casket, was due to be driven around the perimeter of the cemetery before being laid to rest at the burial site in a non-denominational service, the UK's Press Association reported.

Litvinenko's wife Marina and their 12-year-old son Anatoly were among the mourners, PA said.

Litvinenko's father Valter, his mother Nina Belyavskaya and his first wife Natalia were also at the ceremony.

Many of Litvinenko's closest friends were attending the service, including Alex Goldfarb, the exiled Russian billionaire Boris Berezovsky, the filmmaker Andrei Nekrasov and the Chechen dissident Akhmed Zakayev.